Device for standardizing shunts



Sept. 1, 192,1. L. BAGET 1,821,785

DEVICE FOR STANDARDIZING SHUNTS Filed July 29, 1930 Patented Sept. 1, 1931 UNITED STATES PATENT OFFICE I LE'oN BAGET, F PARIS, FRANCE, ASSIGNOR T0 ooimrAeNIE nn'rnonurrs CHIMIQUES ET ELEGTROMETALLURGIQUES ALAis, FROGES ET CAMARQUE, or EARIS,FRA1\TGE, A

CORPORATION OF FRANCE DEVICE FOR STANDARDIZING SHUNTS e Application filed July 29, 1930, Serial no.

The present invention has for itsobj'ect' a method and device for standardizing high intensity shunts (up to 30,000 amperes) used with direct current. 1 i

5 Measuring direct current high intensities is actually effected by a method which consists in opposing, to the flux produced in a magnetic circuit by the conductor through which flows the high intensity current a flux by means of a rheostat 6.

' produced by a winding disposed onthe same magnetic circuit. A r'otatingarmature, disposedin the magnetic circuit, and provided with a measuring apparatus connected to its terminals,serves to indicate when these two fluxes annul each other. When this condition is obtained,there isbut to measure thef current that'flows through the winding for deducing therefrom the current intensity in the conductor disposed in the magnetic circuit.

This method is also applied forcjstandard izing shunts, but it has thedisadva-ntage of necessitating a very accurate standardization of the millivoltmeters that are to be connected to the shunts to be verified and ofthe ammeter that serves tomeasure the current intensity through the winding.

The method and device according to the present invention eliminate the necessity of I these standardizations and the causes of errors that result therefrom.

This method consists in comparing the high intensity shunts to standard shunts through a difierential galvanometer, this comparison being made possible by inducing in a magnetic circuit two opposed fluxes, one produced by the high intensity current, and

the other by a winding connected in series with the standard shunt and by so regulating the current through said winding that the two fluxes annul each other.

The method for standardizing high intensity shunts is thus very much simplified, owing to the fact that it makes it possible to directly measure the error of the shunt to be standardized, provided that a suitable ratio of the standard shunt to the shunt to be stand- V p reafds fi thus directly g ving the error of the ardized be chosen.

An embodimentv of my invention will be described with reference to the appended drawing, which diagrammatically shows a of a diiferential galvanometer 10.

471,570,- and in France October 15, 1929.

standardizing device according to my invention. r. p 1 7 The conductor 1, through which flows the high intensity directcurrent, is surrounded by the magnetic circuit 2. The shunt to be standardized is shown in 3, The magnetic" the difl erent values or shunts that'are to be verified, is connected in series with winding 4:. The terminals of shunts 3 and 7 are re spectively connected tothe windings 8 and 9 rte-rotating armature l1, actuated by a motor, is nserted in the magnetic circuit, and a mlllivoltmeter 12is connected to the terminals of said' armature. An; ammeter 13 serves to measure the 1ntens1ty'iin order to determine the value of current I. a a The current in winding 4 is given a direction and a value such that thefiux produced by said winding in thermag-netic' circuit 2 jmay neutralize the flux produced by the conductor The millivoltmeter 12 makes it possible to 'find out when this condition is iulfilled. 7 At this time there is a constant ratio otinten'Sity Ito intensity i;

.For instance, if I=20,000 amperes and acco'unt of the variationswof current I, one

compares th-etension U to the tension ugiven by standard shunt 7 by means of the differential galvanom eter 10.

,If U= u, the difi'erential galvanometer readszero. V it v If 'u'=.U th differential galvanometer shunt to be verified. 1 V v p r r uhas beenchosen equal to 100, this er- "ror' will be given in per cent.

When, accordin to the usual method, z' and I are measurec (through it and U), the error in the measure is the sum of the er rors in the measures of (uU) and of u, said errors being of the first order.

(in the contrary, according to the invention, is directly measured and the error is reduced to that of the diiierential galvanometer, which is of the second order.

On account of the residual magnetism in the magnetic circuit, the method consisting to oppose the fluxes could give inaccurate results due to the fact that the zero graduatien of the galvanometer does not correspond any longer to the neutralization of the opposed fluxes produced by i and I alone.

In order to obviate this drawback, the ourrent I is cut off and the magnetic circuit?) is saturated by means of thewinding 4; then the current in said winding is decreased to a value for which the flux detectin system indicates that the flux is zero, At t is time,

' the value i of the current is equal to the abscissa at the origin of the hysteresis cycle.

There is but to mark it in absolute value on the difierential galvanometer. This quantity is thus. automatically su tracted from the "a e 1. when u-U is read,

While I have disciosed what I d em to h the preferred. embod m nt of my inventi n, 1 do n t Wish to be limited thereto as there might be hang s made in the disposition and form of the different elements of m device without depart ng from the princip e of my invention as comprehended within he see e of the appended claims. For instance, to differential galvanometer could be of any ty e, and the different apparatus in the d v fe in any suitable manner.

What I claim is: a

1. The method for standardizin a shunt connected to a conductor through w ich flows a high intensity direct current, which consist in inserting the shunt to he verified and a standard shunt respectively in two circuits adapted to induce equal and opposite fluxes in the same magnetic circuit and in comparing said shunts by means of a differential galvanometer.

2. The method for standardizing a shunt connected to a conductor through which fiows a high intensity direct current which consists in disposing a magnetic circuit about said conductor, producing in said magnetic circuit a flux opposed to that induced by said conductor by means of a Winding connected in series to a standard shunt, regulating the current through said winding so that the resultant flux in the magnetic circuit is zero,

and then comparing the shunt to be verified with the standard shunt by means-of a. differential gal anometer, whereb the differenc between the said shunts may Q dir ctly road on the galvanometer.

3. The device for standardizing a shunt measuring the current through said armature,

a winding on said magnetic circuit adapted to produce therein a flux opposed to that )roduced by the conductor, means for fee ing said Winding, a standard shunt connected in series With said winding, means for regulating the current through said winding, and a differential galvanometer adapted to be connected on the one hand with the standard shunt and on the other hand with the shunt to be standard zedei, The device for standardizin a shunt connected to a conductor through which flows a high intensity direct current, said device comprising a magnetic circuit adapted to be mounted about the conductor to which the shunt to be verified is connected, a rotatable armature inserted in said circuit, means for measuring the current through said armature,

a winding on said magnetic circuit adapted" .to produce therein flux opposed to that proof said galvanometer being so displaced with res ct to the true zero point as to automatical v compensate for the residual magnetism in t e magnetic circuit.

In testimony whereof I have signed my. name to thls specification.

LEON BAGET. 

